1. Field of the Invention
This invention relates to an electric signals supplying device in solenoid valve, for supplying electric power in a double-solenoid type valve having two solenoid coils.
2. Related Art Statement
The double-solenoid type valve has two solenoid coils for operating a valve body. For this type solenoid valves, as described in Japanese Utility Model Laid-Open No. 4-129981, such valves have been made that the opposite end portions of a valve housing are respectively provided with a solenoid coil, and that one end portion of the valve housing is only provided with two solenoid coils.
In the solenoid valve of this type having two solenoid coils, the number of terminals of coils is four in one solenoid valve. When a plurality of solenoid valves are mounted on a manifold block, the number of terminals of coils in a manifold solenoid valve, as described in the above-mentional Utility Model, amounts to a considerable number.
In order to save the number of wirings, there has been used a common terminal through which terminals on the same polarity of the respective coils are connected to.
For realization of saving the number of wirings, there has heretofore been practiced that two terminals on one of the polarity of the two coils are connected through a common terminal to a base plate mounted on a solenoid section of a solenoid valve, so that one contact connected to the common terminal is provided on a connector side.
In many solenoid valves, a terminal on the plus polarity of each of solenoid coils is used as a common terminal, and electric signals of the minus polarity for operating the solenoid valve are delivered to each of the terminals on the minus polarity side. In contrast thereto, there is a case where the terminal on the minus polarity side is used as the common terminal, and the electric signals of the plus polarity side are delivered to the terminal on the plus polarity side so as to operate the solenoid valve.
Which polarity is to be selected as the common terminal depends on how a fluid-pressure circuit having a solenoid valve is controlled. That is, some control circuits operate the solenoid valve by the electric signals of the minus polarity and the others operate it by the electric signals of the plus polarity. Accordingly, when the polarity of a control signal is changed due to changes of a production line or a production system in a factory where the solenoid valve is used, the polarity of the control signal is fixed in the solenoid valve, so that it becomes necessary to abandon the solenoid valve operated by the electric signals of the original polarity and change it over to the solenoid valve operated by the electric signals of the other polarity.
Furthermore, even when the solenoid valve is produced, it becomes necessary to prepare one solenoid valve operable on the signal of the plus polarity side and the other solenoid valve operable on the signal of the minus polarity side depending on the users, whereby not only the line for producing the solenoid valve but also handling of parts become complicated.